There are many instances when it is desirable to inexpensively divide units of time or units of distance into smaller units. For example, in a range detector, the time elapsed between the outgoing signal and the incoming signal may be very short, on the order of nanoseconds, and the use of a standard reference clock to count the time elapsed would yield an inaccurate count resulting in inaccurate distance calculations.
In another example, in laser printers, it is often desirable to provide a transition from white to black (or vice versa) at various distances within a given line cell for high resolution. See U.S. Pat. No. 5,109,283 incorporated herein by this reference. A white-to-black or black-to-white signal, however, clocked at the printer's pixel clock rate of 10 MHz, is not resolved finely enough at the printer's laser diode to accurately control print transitions within a given print cell. Faster clocks are too expensive and/or not available to reference the print transitions at the high temporal resolution (e.g., one nanosecond corresponding to print cell distances on the order of microns) required for high resolution graphic images.
One solution to the above problems is to use a device incorporating a free-running ring oscillator (also referred to interchangeably as a loop oscillator). U.S. Pat. Nos. 5,793,709 and 5,903,522 describe such solutions, and are herein incorporated by this reference. However, as signal requirements for applications hi the fields of CD-RW, DVD, communications and radar demand transition edges of higher frequency and precision, limitations are realized. Differences in circuit conductive path lengths and implementation hardware become noticeable. An algebra clock based on the frequency of the reference clock limits the speed of the calculations made by the algebra circuitry. External circuitry calculating the speed of the free-running loop oscillator (“loop”) also limits the speed of the calculations made by the algebra circuitry. Devices using the output may not tolerate a sudden, unpredictable transition in the output signal when a synchronization signal is used.
The present invention addresses these needs.